Maureen
Maureen you've raised an interesting question. In response, I offer a completely uninformed view based on speculation. Astronomers see events all the time that happened millions of years before they were born because it has taken millions of years from the light of the events they see to reach their eyes. We see something when the light of that event reaches our eyes, not when that event happened.
You've also made me think of something I hadn't thought of before. Some interpreters of LDS theology claim that Christ's atonement covered all peoples, times, places and worlds that were, are and will be. This might or might not be true. But if it is true, such an atonement would completely obviate the need for any other atonement, including any possible atonement that might have previously been made by God in some other life. Or if God had previously made some sort of atonement, it must have been limited in scope, and in that sense, lesser than the atonement later made by His Son. So either:
the atonement made by Christ does not cover all time and all places, or
God the Father did not make an atonement, or
God the Father's atonement, if there was one, was lesser than the atonement made by His Son, and therefore another atonement was needed or
Some people, times, and places are covered by more than one atonement.
I'm not sure which of the above possibilities are true or false, but they can't all be true.